1. Field of the Invention
This invention relates to a reproduction apparatus and a reproduction method which can play back both of a first optical disc wherein wobbles of a first predetermined frequency are formed on the opposite side faces of a groove or a land and a second optical disc wherein wobbles of a second predetermined frequency are formed on one side face of a groove or a land.
2. Description of the Related Art
Conventionally, a disc called mini disc (Mini Disc: trademark) is known wherein grooves wobbled at a predetermined frequency are provided in advance on a magneto-optical disc of a diameter of 64 mm and data are recorded on the wobbled grooves.
The mini disc mentioned above has address information recorded in a predetermined modulated condition on the grooves. Access control for the mini disc or retrieval of a recordable area of the mini disc is performed based on the address information.
The mini disc described above allows recording of a compressed audio signal for 74 minutes in the maximum and is considerably superior in convenience because it is superior in portability and exhibits a high access rate. A mini disc for an audio use may be hereinafter referred to simply as MD-DA (Mini Disc Digital Audio).
However, since the mini disc described above only has a limited recording capacity of FE production circuit 140 Megabytes, it is not sufficient to record a video signal thereon.
Further, while a format called MD-DATA1 is known as a format to be used to record computer data onto the mini disc, it is disadvantageous in that the rate in rewriting and reproduction operations is low because the recording density of it is as low as FE production circuit 140 Megabytes and the minimum recording data length is comparatively large.
It is an object of the present invention to provide a reproduction apparatus and a reproduction method by which servo controls suitable for different magneto-optical discs can be performed to allow reproduction of both of a magneto-optical disc having the conventional data format MD-DA and MD-DATA1 and another magneto-optical disc having the new data format MD-DATA2 for higher density recording.
In order to attain the object described above, according to an aspect of the present invention, there is provided a reproduction apparatus for selectively playing back a first optical disc wherein two side faces of each of grooves or lands formed thereon are wobbled at a first frequency and information is recorded on the wobbled grooves or lands and a second optical disc wherein one of two side faces of each of grooves or lands formed thereon is wobbled at a second frequency while the other side face of each of the grooves or lands is formed as a flat face and information is recorded on the grooves or lands, comprising an optical head for irradiating light upon a predetermined one of the grooves or lands and those of the lands or grooves adjacent the predetermined groove or land, first detection means for detecting reflected light from the predetermined groove or land, second detection means for detecting reflected light from the lands or grooves adjacent the predetermined groove or land, first calculation means for calculating a difference between the reflected light of the first detection means and the reflected light of the second detection means to produce a first tracking error signal, second calculation means for calculating a difference between the reflected light from one and the reflected light from the other of the lands or grooves adjacent the predetermined groove or land detected by the second detection means, discrimination means for discriminating whether an optical disc loaded on the reproduction apparatus is the first optical disc or the second optical disc, and tracking controlling means for performing, when the discrimination means discriminates that the loaded optical disc is the first optical disc, tracking control based on the first tracking error signal produced by the first calculation means, but performing, when the discrimination means discriminates that the loaded optical disc is the second optical disc, tracking control based on the second tracking error signal produced by the second calculation means.
According to another aspect of the present invention, there is provided a reproduction apparatus for selectively playing back a first optical disc wherein two side faces of each of grooves or lands formed thereon are wobbled at a first frequency and address information is recorded on the wobbled grooves or lands in advance and a second optical disc wherein one of two side faces of each of grooves or lands formed thereon is wobbled at a second frequency while the other side face of each of the grooves or lands is formed as a flat face and address information is recorded on the grooves or lands in advance, comprising an optical head for irradiating light upon a predetermined one of the grooves or lands and those of the lands or grooves adjacent the predetermined groove or land, detection means divided into at least two regions in a tracing direction of the optical head for detecting reflected light from the predetermined groove or land and the adjacent lands or grooves, first calculation means for adding detection outputs of the at least two regions of the detection means, second calculation means for subtracting a first one from a second one of the detection outputs of the at least two regions of the detection means, discrimination means for discriminating whether an optical disc loaded on the reproduction apparatus is the first optical disc or the second optical disc, selection means for switchably selecting one of the first calculation means and the second calculation means, controlling means for controlling the selection means so that, when the discrimination means discriminates that the loaded optical disc is the first optical disc, the first calculation means is selected, but when the discrimination means discriminates that the loaded optical disc is the second optical disc, the second calculation means is selected, address extraction means for extracting address information based on an output of the first or second calculation means selected by the selection means.
According to a further aspect of the present invention, there is provided a reproduction method for selectively playing back a first optical disc wherein two side faces of each of grooves or lands formed thereon are wobbled at a first frequency and information is recorded on the wobbled grooves or lands and a second optical disc wherein one of two side faces of each of grooves or lands formed thereon is wobbled at a second frequency while the other side face of each of the grooves or lands is formed as a flat face and information is recorded on the grooves or lands, comprising the steps of discriminating whether an object optical disc of playback is the first optical disc or the second optical disc, and producing, when it is discriminated by the discrimination step that the object optical disc is the first optical disc, a tracking error signal based on a side beam and performing tracking control based on the produced tracking error signal, but producing, when it is discriminated by the discrimination step that the object optical disc is the second optical disc, a tracking error signal based on a main beam and a side beam and performing tracking error control based on the produced tracking error signal.
The above and other objects, features and advantages of the present invention will become apparent from the following description and the appended claims, taken in conjunction with the accompanying drawings in which like parts or elements denoted by like reference symbols.